1. Field of the Invention
The present invention relates to a method for securing an end of a headbox flow tube to an end plate. More specifically, the present invention relates to a method and apparatus for securing an end of a headbox flow tube to an end plate of a headbox for a papermaking machine.
2. Information Disclosure Statement
In the papermaking art, stock is ejected from a headbox onto a moving fourdrinier wire such that water within the stock drains through the fourdrinier wire for forming a web on the top surface of the wire.
The headbox is supplied with pressurized stock and essentially includes a tapered header for supplying the stock to a plurality of headbox flow tubes arranged as a tube bank. The stock flows through each of the flow tubes so that the stock is divided into a plurality of parallel flow paths.
The stock emerging from the flow tubes is guided through a slice chamber towards a slice lip at the downstream end of the slice chamber, where the stock is ejected onto the fourdrinier wire.
The plurality of flow tubes are supported within the headbox by an end plate which supports the downstream end of each of the flow tubes. The arrangement is such that the tubes are arranged in horizontal rows, each row being spaced vertically relative to an adjacent row.
Trailing elements are pivotally secured within the end plate such that each row of flow tubes is separated by a trailing element. The arrangement is such that the flow of stock through the slice chamber is divided according to the number of rows of the flow tubes.
In prior art headboxes, the flow tubes were typically of circular cross-sectional configuration at both the upstream and downstream ends thereof.
However, as disclosed in co-pending patent application Ser. No. 07/772,521 to Shands et al, it has been found extremely advantageous to provide the downstream end of such headbox flow tube with a rectangular cross-sectional configuration.
More specifically, the downstream portion of the flow tube progressively changes from a circular cross-sectional configuration to a rectangular shaped configuration adjacent to the downstream end of the tube.
Accordingly, in the prior art flow tube, during the manufacture of a tube bank, the end plate was drilled and machined to a circular configuration for the reception therein of the circular end of a corresponding flow tube. Hydraulic expansion means such as a mandrel of the like were used to expand the end of the headbox flow tube to form a wedge fit within the end plate. Subsequently, the end of the flow tube was welded to the end plate.
However, with the advent of the aforementioned rectangular end type flow tube, the aforementioned method of manufacture becomes inoperative.
The present invention provides a method for laser cutting the end plate of a headbox tube bank for the reception therein of the end of the flow tube, such that the flow tube can be laser welded to the end plate, thereby providing a water tight seal therebetween.
Therefore, it is a primary objected of the present invention to provide a method for securing an end of a headbox flow tube to an end plate that overcomes the aforementioned problems associated with the prior art methods, and which makes a considerable contribution to the art of building of a headbox tube bank.
Another object of the present invention is the provision of a method for securing an end of a headbox flow tube to an end plate which inhibits heat deformation of the flow tubes.
Another object of the present invention is the provision of a method for securing an end of a headbox flow tube to an end plate which avoids the necessity for the provision of welding fillers and the like between the end plate and the flow tube.
Other objects and advantages of the present invention will be readily apparent to those skilled in the art by consideration the detailed description contains hereinafter, taken in conjunction with the annexed drawings.